Prosthesis stem



FIG. 1 is a rear elevation of a prosthesis stem showing my new design;

FIG. 2 is a front elevation thereof;

FIG. 3 is a side elevation thereof;

FIG. 4 is a side elevation of the side opposite that shown in FIG. 4;

FIG. 5 is a perspective thereof;

FIG. 6 is a bottom perspective thereof; and,

FIG. 7 is a top perspective view thereof.

The ornamental design for a prosthesis stem, as shown and described. 